1. Field of the Invention
The present invention relates to a non-halogen flame retardant styrene resin composition. More particularly, the present invention relates to a non-halogen flame retardant styrene resin composition which comprises (a) a styrene resin and (b) a phosphorous-modified epoxy resin and thus exhibits superior flame retardancy to external candle flame ignition.
2. Description of the Related Art
In general, an acrylonitrile-butadiene-styrene (hereinafter, referred to as ABS) resin is widely used as an exterior material of electric/electrical products and office machines and the like due to stiffness and chemical resistance of acrylonitrile, and processability and mechanical properties of butadiene and styrene. However, the ABS resin is inherently readily combustible and thus does not almost have flame retardancy.
Due to these problems, the ABS resin used for electrical and electronic products, office machines and the like should satisfy flame-retardancy standards in order to secure safety to flame of electrical and electronic products.
Methods for imparting flame retardancy to ABS resins include polymerization of rubber-modified styrene resins through incorporation of flame-retardant monomers, mixing a flame retardant and an auxiliary flame retardant with the prepared rubber-modified styrene resin and the like. Examples of the flame retardant include halogen flame retardants and non-halogen flame retardants such as phosphorous, nitrogen and hydroxide flame retardants, and examples of the auxiliary flame retardant include antimony compounds, zinc compounds, polysiloxane compounds and the like. However, when halogen flame retardants are used, corrosive toxic gases such as HBr and HCl are generated due to high temperature and pressure entailed during processing of ABS resins, thus disadvantageously having negative effects on work environment and human. This problem is disadvantageously generated during combustion of ABS resins comprising a halogen flame retardant.
Accordingly, research to solve these problems is actively underway. Phosphorus flame retardants attract the most attention in terms of environment, efficiency and cost.
However, phosphorous flame retardants should be added in amounts higher than halogen flat retardants and generally exhibit flame retardancy by solid phase reaction. Accordingly, a char former should be also added in an excessive amount when it is difficult to generate char using a base rein. During this process, physical properties of the base resin may be greatly damaged and an approach for minimizing amounts of added phosphorous flame retardants and char former is thus required.
Meanwhile, there is a vertical combustion test method in accordance with UL94 associated with a flame retardant standard and a flame retardancy identification test method. This test method is a standard to evaluate flame resistance against internal combustion caused by short circuit or the like of a circuit substrate present in electronic products. Meanwhile, an external candle flame ignition standard (related standard: IEC TS 62441) which is standardized is a standard through which flame resistance of a final product is evaluated, when a candle as an exterior ignition source comes in contact with the electronic product due to changes in external environments.
The external candle flame ignition standard is utilized in a wider range of applications since subjects to which the standard is applied are all combustible materials and is more realistic since the standard presumes a case of flames of burning candles as fires which may often be generated in houses.